1. Field of the Invention
This invention relates to a carrier of a catalyst for the production of an epoxide, a catalyst for the production of an epoxide, and a method for the production of an epoxide. More particularly, it relates to a carrier to be used for a catalyst for the production of an epoxide by subjecting a corresponding unsaturated hydrocarbon having 2 to 4 carbon atoms to gas phase partial oxidation with a molecular oxygen-containing gas, a catalyst for the production of an epoxide obtained by using this carrier, and a method for producing an epoxide by subjecting a corresponding unsaturated hydrocarbon having 2 to 4 carbon atoms to gas phase partial oxidation with a molecular oxygen-containing gas in the presence of this catalyst for the production of an epoxide.
2. Description of the Related Art
The catalyst for the production of an epoxide by the gas phase partial oxidation of a corresponding unsaturated hydrocarbon having 2 to 4 carbon atoms with a molecular oxygen-containing gas is required to possess high selectivity, high activity, and long life as the properties for performance. With the object of improving these properties, therefore, various studies have been made to date concerning carriers for catalysts for the production of epoxides, reaction promoters, conditions of heat treatment, and the like.
JP-A-55-145677, for example, discloses a silver catalyst which is obtained by depositing silver and optionally an alkali metal component or an alkaline earth metal component on a nonacidic carrier containing alumina, silica, and titania in a total concentration of not less than 99 mass % and metals of the groups of 5A, 6A, 7A, 8B, and 2B in the Periodic Table of the Elements (hereinafter designated as “IUPAC”) in a total concentration of less than 0.1 mass % as reduced to metal oxides, having a pKa of +4.8, and not allowing methyl red to impart an acid color thereto and calcining the produced composite material in a current of air or hydrogen at a temperature in the range of 100°–1000° C.
U.S. Pat. No. 4,701,437 discloses a silver catalyst for the production of ethylene oxide which is characterized by using a carrier formed by adding 1–30 mass % of a tin compound to alumina.
JP-A-04-363139 discloses a silver catalyst for the production of ethylene oxide which is characterized by using a carrier obtained by adding a compound containing at least one element selected from the class consisting of the elements of the 3A–7A groups and the 3B–5B groups and the fourth, fifth, and sixth periods in the Periodic Table of the Elements to α-alumina and firing the resultant mixture.
U.S. Pat. No. 5,077,256 discloses a silver catalyst for the production of ethylene oxide which is obtained by precipitating silver and 0.001–0.05 gram-equivalent weight of a cesium compound as a reaction accelerator based on the weight of the perfected catalyst on a carrier having α-alumina as a main component and containing 3×10−4–2×10−1 g of amorphous silica as reduced to Si atom per g of the carrier and subsequently subjecting the resultant composite material to a heat treatment in an inert gas containing oxygen at a concentration of not more than 3 vol. % at a temperature in the range of 400°–950° C.
The specification of U.S. Pat. No. 4,039,561 discloses the fact that the addition of Sb as a reaction promoters is effective when the addition is made during the preparation of a catalyst, not during the preparation of a carrier. The atomic ratio is not more than 0.15 of Sb to 100 of Ag.
U.S. Pat. No. 4,389,338 discloses a silver catalyst for the production of ethylene oxide, characterized by the catalyst being obtained by depositing silver and an alkali metal and/or thallium as a reaction accelerator on a carrier and subjecting the resultant composite material to a high-temperature heat treatment in an inert gas having an oxygen concentration of not more than 3% at a temperature in the range of 500°–950° C.
The aforementioned known catalysts for producing epoxides such as ethylene oxide are still deficient in such properties as selectivity. Thus, the desirability of further improving the properties of these catalysts has been finding recognition.
One object of this invention, therefore, is to provide an improved carrier for the production of an epoxide, specifically a carrier for the catalyst for the production of an epoxide, the carrier being such that the use thereof enables production of a catalyst excelling in such properties as selectivity.
Another object of this invention is to provide a catalyst for the production of an epoxide which excels in such properties as selectivity.
Still another object of this invention is to provide a method for the production of an epoxide which enables the epoxide to be produced industrially advantageously as by dint of high selectivity.